The performance and operation of a modern vehicle is often monitored using vehicle diagnostic tools. These tools can receive information from the vehicle and use the information to generate a diagnosis that is understandable by professionals servicing the vehicle. In one example, a vehicle technician can use the vehicle diagnostic tool to access any diagnostic trouble codes (DTCs) that the vehicle has generated and possibly interpret the DTCs in a way that explains a vehicular problem to the technician. While vehicle diagnostic tools can be helpful for servicing vehicles, it can also be helpful to control access to the information carried by the vehicle or its various modules.